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EPA 2003 Blind Audit of Protocol Gases

EPA 2003 Blind Audit of Protocol Gases. John Schakenbach, USEPA, CAMD Scott Shanklin, Cadmus Group Bob Wright, USEPA, ORD EPRI CEM User Group Milwaukee, WI May 4-6, 2004. What is the Problem?. Historically, blind audits of calibration gases have shown poor quality initially

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EPA 2003 Blind Audit of Protocol Gases

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  1. EPA 2003 Blind Audit of Protocol Gases John Schakenbach, USEPA, CAMD Scott Shanklin, Cadmus Group Bob Wright, USEPA, ORD EPRI CEM User Group Milwaukee, WI May 4-6, 2004

  2. What is the Problem? • Historically, blind audits of calibration gases have shown poor quality initially • SO2 RATA using plant’s incorrect cal gas (low by 15%). Source could underreport SO2 by 15% and be undetected for at least 6 months.

  3. Other Reasons Why Accurate Cal Gas is Important • Only daily assurance CEM is really working • Reference Method analyzers need accurate calibration gases to produce accurate RATA results

  4. Purpose of Blind Audits • Help vendors improve gas quality • Help sources identify good vendors

  5. History • 1970’s -1996 EPA audited gases • Posted results • In 1995, one vendor off by -16.3% (CEM would underreport) • Strong utility and vendor support • Auditing strongly correlated with improved gas quality

  6. Current Gas Analysis • First audit in 7 years • Blind audit • 14 national gas vendors • Similar procedures as in past • SRMs and NTRMs used • 42 Protocol tri-blend cylinders • MACTEC (UV and NDIR) and Spectral Insights (FTIR)

  7. Tri-blend Protocol Gases

  8. Instrumentation • NO - API Model 200AH chemiluminescence • NO - AMETEK Model 922M differential absorption UV • SO2 - Bovar Model 721M differential absorption UV • CO2 - California Analytical Model 3300A NDIR • NO, SO2 and CO2 - Nicolet Nexus Model 760 FTIR • Environics (Graseby-Nutech) Series 3740 gas dilution system

  9. Gas Manifold/Regulator Vent Vent Vacuum Pump Manifold Vent Valve Toggle Valves Selector Valve Check Valves Vent Isolation Valves Transducers P T Cell Computer FTIR Spectrometer Candidate, Zero, SRM or NTRM Gas Standards Spectral Insights Assay Apparatus

  10. Accuracy Criterion • Part 75, Appendix A, sec 5.1.4 requires 2.0% of tag value • Protocol procedures achieve +2% of tag value: 1% Standard Reference Material plus 1% EPA Protocol methodology

  11. Problems • CO2 quenching biased the NO concs from chemiluminescent analyzer low • Chemiluminescent NO concs thrown out • Measurements repeated with a UV analyzer • UV analyzer was set up for 0 - 500 ppm NO, but should have been for 0-1000 ppm • Threw out high level NO concs • Repeated high level NO measurements using FTIR

  12. Problems • SO2 interfered with UV analyzer NO readings • Injected SO2 in N2 to develop a correction • Ran out of high level CO2 SRM for FTIR • Threw out the high level CO2 FTIR results and relied on NDIR

  13. Results • EPA presents the following information without assigning a rating to the gas vendors. • If EPA’s and vendor’s values differ by 2.0% or less, then because of uncertainties in the measurement system, statistically, there is no difference between the two values, e.g., a difference of 2.0% and 0.5% are considered equal. • All vendors that failed are re-analyzing their gas cylinders. When EPA receives the re-analyzed results, they will be posted.

  14. Results • Overall failure rate: 14 of 126 analyses (11%) • 57% of vendors failed • SO2: Worst tag value ~2.5% high • NO: Worst tag value ~8% low • CO2: Worst tag value ~4.9% high • All 42 cylinders met the Protocol Procedure documentation requirements

  15. NO Analyses SO2 Analyses CO2 Analyses UV FTIR Both UV FTIR Both NDIR FTIR Both Low 6/14 4/14 4/14 6/14 1/14 1/14 1/14 1/14 1/14 Mid 2/14 3/14 2/14 0/14 0/14 0/14 0/14 1/14 0/14 High - - - 3/14 - - - 0/14 3/14 0/14 3/14 - - - - - - EPA Protocol Gases not meeting Acceptance Criterion

  16. Percent Failure Rate by Vendor Technology

  17. Lessons Learned • Detailed standard operating procedures for analyzing single and multicomponent mixtures are needed in EPA’s Protocol Procedures, especially for FTIR • First ensure lab can correctly analyze single component cylinders • Then check for interferences by measuring a multicomponent cylinder simultaneously with analyzers for each component gas • Use an SRM or NTRM to get reference spectrum for FTIR measurements

  18. Audits Can Be Effective 1992 1993 1994 1995 1996 2003

  19. Audit Program Issues • Scope • Stringency • Structure

  20. Options - Scope • Part 75 only • All source-level programs, e.g., Part 75, NSPS, SIP, NSR • All source and ambient-level programs

  21. Options - Stringency • Work with vendors to fix problems • Work with vendors and post audit results on web sites • Formal gas vendor certification program

  22. Options - Structure • Spin-off to 3rd party (A2LA, NVLAP, NSF, etc.) to purchase and analyze cylinders (set up fee-based system) with EPA oversight • Through EPA task order, contractor purchases and analyzes cylinders from major suppliers (EPA used to do this) • Other (NELAC, gas vendor-developed mechanism, NIST, EPA lab, etc.)

  23. Initial Recommendations Scope All source and ambient-level programs Stringency Work with vendors; post audit results Structure Set up fee-based system to purchase and analyze cylinders using 3rd party with EPA oversight; or possibly use gas vendor-developed mechanism

  24. Example 3rd Parties for Spin Off • American Association for Laboratory Accreditation (A2LA) • National Voluntary Laboratory Accreditation Program (NVLAP) • National Sanitation Foundation (NSF)

  25. Next Steps • Get more feedback from gas vendors and other interested parties

  26. For a Copy of Presentation www.epa.gov/airmarkets, click on “Recent Additions” near top left corner or John Schakenbach Phone: 202-343-9158 schakenbach.john@epa.gov

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